Preparation of alpha-chlormethyl naphthalene



ee. rear NETD PREPARATION OF e-CHLOBMETHYL NAPHTHALENE Adrien Cambron,Ottawa, Ontario, Canada, as-

signor to The Honorary Advisory Council for Scientific and IndustrialResearch, ttawa,0ntat-i0, Canada, a corporation of Canada No Drawing.

This invention relates to naphthyl acetic acid, its esters and salts andmore particularly to an improved method of producing a-naphthyl aceticacid. its esters and salts.

The object of the invention is to provide a method whereby thesecompounds may be produced at much reduced cost in order that they maybemade widely available for uses for which they are well adapted, as forexample in the stimulation of germination and growth in seeds, plantsand the like.

In accordance with the invention dichlormethyl ether is caused to reactwith naphthalene in the presence-of an acid condensing agent, such asphosphoric or sulphuric acid and water, to yield s-chlormethylnaphthalene. This reaction proceeds best at a temperature of about 100C. at ordinary pressures and when the mixture is kept well stirred inthe reacting vessel. The corresponding acetonitrile is formed by knownmethods and the acetonitrile is heated with acetic acid in the presenceof water and an acid hydrolyzing agent, such as sulphuric or phosphoricacid, to form the a-naphthyl acetic acid.

As illustrative of the detailed procedure found to give best results thefollowing description is given. While one may begin with dichlormethylether the following illustrates the preferred procedure.

A mixture of 180 grams paraform, 750 cubic centimetres of glacial aceticacid and 576 grams naphthalene is heated, with stirring, to 98 to 100 C.and a mixture of 562.5 grams concentrated hydrochloric acid (37%) and135 cubic centimetres syrupy phosphoric acid is added during a period often to fifteen minutes while heating at 100 C. is continued for a periodof 3 hours with eificient stirring. The reaction mixture is poured into3 litres of cold water and the water is decanted leaving the oilyproduct which constitutes the lower layer. It is then washed by stirringtwo or three times with three litres of cold water, filtered from asmall amount of solid insoluble product, and distilled in vacuum giving400 grams or a 60% yield of u-chlormethyl naphthalene based on thenaphthalene consumed.

The a-chlormethy. naphthalene is converted to the correspondingacetonitrile by known methods, as by refluxing for an hour with asolution of 225 grams of potassium cyanide in 1250 cubic centimetres ofethyl alcohol and 400 cubic centimetres of water. The alcohol isdistilled off and the liquid product is washed with water, and is thenextracted with ether. The extract is dried and filtered and the ether isdistilled ofi, yielding Application September 29, 1938, Serial No.232,289

' (Cl. zen-s49) crude a-naphthyl acetonitrile. By vacuum distillation,the pure nitrile may be obtained and purification of the nitrile at thisstage renders the purification of the final product easier.

There is then added to the crude or the puriesters may be formed byreplacing the acetic acid with an alcohol. That is, the acid hydrolysisof the nitrile is effected in the presence of an alcohol.

The a-naphthyl acetic acid may be purified by dissolving in 50% alcoholsolution and treating the solution, while boiling, with charcoal. It maybe again precipitated with cold water, filtered and dried. A yield of263 grams of pure naphthyl acetic acid having a melting point of 131 C.is thus obtained from 400 grams of a mixture of 562.5 grams ofconcentrated hydro-' chloric acid and c. c. of syrupy phosphorica-chlormethyl naphthalene.

Alternatively the acid may be purified by dissolving in moderatelyconcentrated caustic alkali solution, filtered from insoluble products,and the pure a-naphthyl acetic acid may then be precipitated by theaddition of excess mineral acid, or the alkalisalt may be obtained byevaporation.

It should be stated that highest yields have been obtained whenphosphoric acid is used in forming the chlormethyl naphthalene but othercondensing agents may be used as previously indicated.

This application is a continuation in part 0 application Serial No.182,000, filed D 27, 1937.

I claim:

1. In the production of alpha-naphthyl acetic acid its esters and saltsthe method which comprises adding syrupy phosphoric acid, as acondensing agent and concentrated hydrochlorie acid to a mixture ofparaform, acetic acid and naphthalene while stirring the mixture at atemperature of about 100 C. to cause the formation of alpha-chlormethylnaphthalene by reaction with dichlormethyl ether formed in situ in thepresence of said condensing agent.

2. A'method as described in claim 1 wherein acid is gradually added to aheated mixture of grams paraform, 750 c. c. of acetic acid and 576 gramsof naphthalene and while stirring the mixture maintaining thetemperature at about 100 C. for a period of substantially three hours toform alpha-chlormethyl naphthalene.

3. In the production of alpha-naphthyl acetic acid, its esters andsalts, the method which com prises heating at substantially 100 C. for aperiod of about three hours paraform, naphthalene and concentratedhydrochloric acid in the presence of acetic acid and as a condensingagent one of the group consisting of sulphuric and phosphoric acids toform alpha-chlormethyl naphthalene.

